WO2023077266A1

WO2023077266A1 - Secondary battery and lithium supplementing method therefor, battery module, battery pack, and electric device

Info

Publication number: WO2023077266A1
Application number: PCT/CN2021/128178
Authority: WO
Inventors: 杨龙飞; 杨丽美; 刘江; 刘晓梅
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2021-11-02
Filing date: 2021-11-02
Publication date: 2023-05-11
Also published as: CN116802867A; EP4207415A1

Abstract

The present application provides a secondary battery and a lithium supplementing method therefor, a battery module, a battery pack, and an electric device. The secondary battery comprises a housing, an end cover assembly, and an electrode assembly, the housing has an opening, the end cover assembly is used for sealing the opening of the housing, and the electrode assembly is packaged in the housing and comprises a positive pole piece and a negative pole piece. The end cover assembly is provided with a first electrode terminal, a second electrode terminal, and a third electrode terminal, and the electrode assembly is electrically connected to the first electrode terminal and the second electrode terminal. The secondary battery further comprises a lithium source, the lithium source is provided on the inner side of the housing and is electrically connected to the third electrode terminal, and the lithium source comprises a lithium metal layer and a metal carrier that is located between the lithium metal layer and the housing and that is used for supporting the lithium metal layer. The present application can accurately control the lithium supplementing rate and the lithium supplementing amount of the secondary battery, and greatly improve the cyclic performance and the storage performance of the secondary battery.

Description

Secondary battery and method for replenishing lithium therefor, battery module, battery pack, and electrical device

technical field

The application belongs to the technical field of batteries, and in particular relates to a secondary battery, a method for replenishing lithium therefor, a battery module, a battery pack and an electrical device.

Background technique

In recent years, with the application and promotion of secondary batteries in various electronic products, new energy vehicles (such as electric buses, passenger cars, taxis, mining trucks, heavy trucks, etc.) and energy storage systems, their cycle life received more and more attention. During the charging and discharging process of the secondary battery, active ions (such as lithium ions) are intercalated and extracted back and forth between the positive electrode and the negative electrode. The formation and destruction of the electrolyte (SEI) film, etc., the active ions are inevitably consumed, resulting in the continuous decline in the capacity of the secondary battery and the difficulty of having a longer cycle life.

Contents of the invention

The purpose of this application is to provide a secondary battery and its lithium replenishment method, battery module, battery pack and electrical device, aiming at precisely controlling the lithium replenishment rate and amount of lithium replenishment of the secondary battery, and greatly improving the secondary battery Cycle performance and storage performance.

The first aspect of the present application provides a secondary battery, including a casing, an end cap assembly, and an electrode assembly, the casing has an opening, the end cap assembly is used to close the opening of the casing, and the electrode assembly is packaged in the casing and includes a positive pole piece and negative pole piece. The end cap assembly is provided with a first electrode terminal, a second electrode terminal and a third electrode terminal, and the electrode assembly is electrically connected to the first electrode terminal and the second electrode terminal. The secondary battery also includes a lithium source, the lithium source is arranged inside the casing and is electrically connected to the third electrode terminal, the lithium source includes a lithium metal layer and a metal carrier positioned between the lithium metal layer and the casing and used to support the lithium metal layer , the third electrode terminal is controllably electrically connected to the first electrode terminal or the second electrode terminal through an external power source, so that the lithium source can replenish lithium to the electrode assembly.

The secondary battery of the present application has simple structure and low production cost. By adjusting the external power supply voltage, current, and power-on time parameters, the rate and amount of lithium replenishment can be precisely controlled, and the electrode assembly can be replenished with lithium evenly and quickly, effectively reducing the capacity loss of the secondary battery and improving the secondary battery capacity. Battery cycle performance and storage performance.

The lithium metal layer is arranged on the metal carrier, and the metal carrier is electrically connected to the third electrode terminal through a wire. Compared with placing the lithium metal layer directly on the inside of the casing, the embodiment of the secondary battery of the present application can improve the utilization rate of the lithium metal layer, and prevent lithium metal from being discharged first in a local area of the lithium metal layer to form lithium ions and then form lithium ions in this local area. Open circuit will affect the use of metal lithium in other areas.

In any embodiment of the present application, the housing includes a bottom plate and a side plate, and the lithium source is arranged inside the bottom plate and/or inside the side plate. Optionally, the lithium source is disposed inside the bottom plate. When the lithium source is placed inside the bottom plate, the surface of the lithium source is parallel to the end face of the electrode assembly, so that the distance between the surface of the lithium source and the pole pieces of each circle of the electrode assembly is the same. It can quickly and evenly insert lithium into each circle of electrode pole pieces. At the same time, when the lithium source is arranged inside the bottom plate, the gravity of the electrode assembly can also be used to achieve good physical compression between the lithium metal layer and the metal carrier, ensuring good electronic conductivity between the lithium metal layer and the metal carrier.

In any embodiment of the present application, the material of the metal carrier is selected from copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy or stainless steel.

In any embodiment of the present application, the secondary battery further includes an insulator between the lithium source and the electrode assembly to separate the lithium source from the electrode assembly.

In any embodiment of the present application, the total capacity C3 of the negative electrode sheet and the total capacity C4 of the positive electrode sheet satisfy C3/C4 of 1.0˜2.1. Optionally, C3/C4 is 1.0-1.3. The total capacity of the negative electrode sheet is greater than or equal to the total capacity of the positive electrode sheet. During the charging and discharging process of the secondary battery, the vacancies provided by the negative electrode active material can fully accommodate the insertion of lithium ions from the lithium metal layer and the positive electrode active material, preventing the interface of the negative electrode from analysing. lithium.

In any embodiment of the present application, the total capacity C3 of the negative pole piece, the total capacity C4 of the positive pole piece, and the theoretical capacity C5 of the lithium metal layer satisfy C3/(C4+C5×K)≥0.2, and K represents the lithium metal layer The middle metal lithium is used to compensate the utilization rate of lithium ions. Optionally, C3/(C4+C5×K) is 0.5˜1.1. The electrode assembly of the present application satisfies the above relationship and can effectively prevent lithium deposition at the interface of the negative electrode, thereby better improving the cycle performance, storage performance and safety performance of the secondary battery.

In any embodiment of the present application, the total capacity C4 of the positive electrode sheet and the theoretical capacity C5 of the lithium metal layer satisfy (C5×K)/C4×100%≥3%. Optionally, (C5×K)/C4×100% is 5%˜100%. The electrode assembly of the present application satisfies the above relationship, the theoretical capacity of the lithium metal layer can meet the actual demand for lithium supplementation, avoiding the excessive mass of the lithium metal layer, causing most of the lithium to be idle and not used for lithium supplementation in the electrode assembly, which not only increases The production cost also reduces the mass energy density of the secondary battery.

The second aspect of the present application provides a lithium supplementation method for a secondary battery, at least including the

following steps

1 and 2.

Step 1, providing a secondary battery. A secondary battery includes a case, an end cap assembly, an electrode assembly, and a lithium source. The housing has an opening. The end cap assembly is used to close the opening of the housing and is provided with a first electrode terminal, a second electrode terminal and a third electrode terminal. The electrode assembly is packaged in the case and electrically connected with the first electrode terminal and the second electrode terminal. The lithium source is disposed inside the case and electrically connected to the third electrode terminal. The lithium source includes a lithium metal layer and a metal carrier located between the lithium metal layer and the case for supporting the lithium metal layer.

Step 2, electrically connecting the third electrode terminal to the first electrode terminal or the second electrode terminal through an external power source, so that the lithium source can replenish lithium to the electrode assembly.

The secondary battery obtained through the lithium supplementation method of the present application has greatly improved cycle performance and storage performance.

In any embodiment of the present application, the external power source is a charging and discharging motor.

In any implementation manner of the present application, the adjustable range of the voltage of the external power supply is 0V˜5V.

In any embodiment of the present application, the energizing current of the external power supply is 0.002A˜50A. Optionally, the current of the external power supply is 0.005A˜0.1A. Using a smaller current to replenish lithium to the electrode assembly can reduce the impact of concentration polarization on the uniformity of lithium replenishment, and using a smaller current to replenish lithium to the electrode assembly can improve the actual utilization of the lithium metal layer, which is conducive to accurate Precisely control the rate and amount of lithium supplementation during each lithium supplementation.

The third aspect of the present application provides a battery module, which includes the secondary battery according to the first aspect of the present application.

A fourth aspect of the present application provides a battery pack, which includes the battery module of the third aspect of the present application.

A fifth aspect of the present application provides an electric device, which includes at least one of the secondary battery of the first aspect of the present application, the battery module of the third aspect, and the battery pack of the fourth aspect.

The battery module, battery pack and electric device of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary battery.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present application more clearly, the following briefly introduces the drawings that are used in the embodiments of the present application. Apparently, the drawings described below are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of an embodiment of a secondary battery of the present application.

FIG. 2 is an exploded schematic diagram of the secondary battery shown in FIG. 1 .

FIG. 3 is an exploded schematic view of another embodiment of the secondary battery of the present application.

FIG. 4 is a schematic diagram of another embodiment of the secondary battery of the present application.

FIG. 5 is a schematic diagram of another embodiment of the secondary battery of the present application.

FIG. 6 is a schematic diagram of an embodiment of the battery module of the present application.

FIG. 7 is a schematic diagram of an embodiment of the battery pack of the present application.

FIG. 8 is an exploded schematic view of the battery pack shown in FIG. 7 .

FIG. 9 is a schematic diagram of an embodiment of an electrical device including the secondary battery of the present application as a power source.

In the drawings, the drawings are not necessarily drawn to scale.

Detailed ways

Hereinafter, embodiments of the secondary battery and its lithium replenishment method, battery module, battery pack and power consumption device of the present application will be specifically disclosed in detail with reference to the accompanying drawings. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known items and repeated descriptions of substantially the same configurations may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

A "range" disclosed herein is defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined in any combination, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the

minimum range values

1 and 2 are listed, and if the

maximum range values

3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5. In this application, unless otherwise stated, the numerical range "a-b" represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values. In addition, when expressing that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

If there is no special description, all the implementation modes and optional implementation modes of the present application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure content of the application.

If there is no special description, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be considered included in the disclosure content of this application.

Unless otherwise specified, all steps in the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence. For example, mentioning that the method may also include step (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and so on.

If there is no special description, the "comprising" and "comprising" mentioned in this application mean open or closed. For example, the "comprising" and "comprising" may mean that other components not listed may be included or included, or only listed components may be included or included.

In this application, the term "or" is inclusive unless otherwise stated. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).

The technical terms "first", "second", "third" and so on are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. In the description of the embodiments of the present application, "plurality" means two or more, unless otherwise specifically defined.

In the description of the embodiments of this application, unless otherwise clearly specified and limited, the technical terms "installation", "connection", "connection", "fixation" and other terms should be understood in a broad sense, for example, it can be a fixed connection, or It can be a detachable connection, or integrated; it can also be a mechanical connection, it can also be an electrical connection; it can be directly connected or indirectly connected through an intermediary, and it can be the internal communication of two components or the interaction of two components relation. Those of ordinary skill in the art can understand the specific meanings of the above terms in the embodiments of the present application according to specific situations.

In recent years, based on the cost of electricity per kilowatt-hour, the requirements for the service life of secondary batteries have become higher and higher. Therefore, effective technical means are needed to improve the service life of secondary batteries and reduce the cost of electricity per kilowatt-hour to meet market demand. At present, the main means to improve the service life of secondary batteries are: selecting positive and negative active materials with good cycle performance and storage performance, optimizing the composition of the electrolyte (for example, changing the type of organic solvent and additives), optimizing the composition of the positive and negative film layers , Optimizing SEI film formation conditions, etc. These means are all considered from the perspective of suppressing negative electrode side reactions. They delay the reduction of active ions by throttling, so they can only play a limited role. There is still a big gap between the goal of new energy vehicles and large-scale energy storage systems with a cycle life of more than 15,000 times.

In order to improve the service life and energy density of the secondary battery, the prior art also proposes the use of lithium supplementation technology to increase the content of active ions and compensate for the irreversible loss of active ions caused by the formation of an SEI film on the surface of the negative electrode active material. At present, the main and highly mature technology is the negative electrode lithium supplementation process, such as covering a lithium metal layer on the surface of the negative electrode with lithium powder or lithium foil. However, the chemical properties of lithium metal are very active, and it is easy to react with moisture in the air. Therefore, the requirements for the environment (air humidity, oxygen content, etc.) and equipment are relatively high in the process of lithium supplementation, which increases the difficulty of the process; It is easy to float in the air, resulting in a high safety risk in the process of lithium supplementation. In addition, the existing technology cannot control the rate and amount of lithium supplementation, so there are safety risks such as excessive lithium supplementation leading to lithium decomposition at the negative electrode interface, and even short circuits in the battery.

In order to solve the above problems, the inventors have improved the structure of the secondary battery, and proposed a secondary battery that can precisely control the rate and amount of lithium supplementation, and has significantly improved cycle performance and storage performance.

secondary battery

Secondary batteries, also known as rechargeable batteries or accumulators, refer to batteries that can be activated by charging the active materials and continue to be used after the battery is discharged. The present application has no special limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape.

The secondary battery of the present application includes a case, an end cap assembly, and an electrode assembly. The casing has an opening, the end cap assembly is used to close the opening of the casing, and the end cap assembly is provided with a first electrode terminal, a second electrode terminal and a third electrode terminal. The electrode assembly is packaged in the case and electrically connected with the first electrode terminal and the second electrode terminal. The electrode assembly includes a positive pole piece and a negative pole piece. The secondary battery of the present application also includes a lithium source, the lithium source is arranged inside the casing and is electrically connected to the third electrode terminal, and the lithium source includes a lithium metal layer and a lithium metal layer located between the lithium metal layer and the casing and used to support the lithium metal. layered metal carrier. The third electrode terminal is controllably electrically connected to the first electrode terminal or the second electrode terminal through an external power source, so that the lithium source can supplement lithium to the electrode assembly. The number of electrode assemblies contained in the secondary battery of the present application can be one or several, which can be adjusted according to actual needs. The material of the housing is not subject to specific restrictions, and may be selected according to actual needs. In some embodiments, the casing may be a hard plastic casing, an aluminum casing, a steel casing, or the like.

The lithium metal layer is arranged on the metal carrier, and the metal carrier can be electrically connected to the third electrode terminal through a wire. Compared with placing the lithium metal layer directly on the inside of the casing, the embodiment of the secondary battery of the present application can improve the utilization rate of the lithium metal layer, and prevent lithium metal from being discharged first in a local area of the lithium metal layer to form lithium ions and then form lithium ions in this local area. Open circuit will affect the use of metal lithium in other areas.

When the third electrode terminal is electrically connected to the first electrode terminal or the second electrode terminal by an external power supply, the lithium metal layer can lithiate the negative electrode active material or the positive electrode active material in the electrode assembly (for example, partially lithiated, or fully lithiated) ), to supplement lithium to the positive or negative electrode of the electrode assembly.

The timing of lithium replenishment for the secondary battery of this application is not subject to specific restrictions, and can be selected according to actual needs. For example, the third electrode terminal is controllably electrically connected to the first electrode terminal or the second electrode terminal through an external power supply, so that it can be used in the secondary battery manufacturing process (for example, before the formation process, after the formation process), and in the secondary battery During the charge and discharge process, storage process, repair process, etc., the lithium source is used to supplement lithium to the electrode assembly according to actual needs.

For example, in the secondary battery preparation process, the third electrode terminal is electrically connected to one of the first electrode terminal and the second electrode terminal that is connected to the negative electrode of the electrode assembly through an external power supply, so that the lithium source is connected to the negative electrode of the electrode assembly. Lithium supplementation compensates for the loss of lithium ions on the surface of the negative electrode active material due to the formation of an SEI film. At the same time, in the process of secondary battery preparation, by adjusting the energizing voltage, energizing current, and energizing time of the external power supply, the lithium source can be used not only to compensate for the lithium ion loss caused by the formation of the SEI film on the surface of the negative electrode active material, but also to Make the negative electrode pre-intercalate lithium and store excess lithium ions; during the charging and discharging process of the secondary battery, this part of excess lithium ions can be released to increase the number of lithium ions that can migrate between the positive and negative electrodes, thereby effectively reducing the capacity of the secondary battery Loss, improve the cycle performance and storage performance of the secondary battery.

For example, during the charging and discharging process, storage process, repairing process, etc. of the secondary battery, according to the attenuation of the discharge capacity of the secondary battery, the third electrode terminal is electrically connected to the first electrode terminal or the second electrode terminal through an external power supply, so as to Make the lithium source supplement lithium to the positive or negative electrode of the electrode assembly, increase the number of lithium ions that can migrate between the positive and negative electrodes, thereby effectively reducing the capacity loss of the secondary battery and improving the cycle performance and storage performance of the secondary battery. In some embodiments, the amount of lithium supplementation may be less than or equal to the decaying capacity of the secondary battery after discharge.

The number of times of lithium replenishment for the secondary battery of this application is not specifically limited, and can be selected according to actual needs. For example, during the preparation process of the secondary battery and during the charging and discharging process, storage process, and repair process of the secondary battery, one or more lithium supplements are performed as required. The amount of lithium supplemented each time is adjusted according to actual needs, for example, by adjusting the external power supply voltage, current, and power-on time and other parameters to accurately control.

In some embodiments, according to actual needs, the external power supply is turned on and the voltage is adjusted to 0V, the third electrode terminal is electrically connected to the first electrode terminal or the second electrode terminal, and the third electrode terminal is connected to the first electrode terminal or the second electrode terminal. The spontaneous voltage difference between the electrode terminals replenishes lithium to the electrode assembly. In some embodiments, according to actual needs, the external power supply is turned on, the third electrode terminal is electrically connected to the first electrode terminal or the second electrode terminal, and then the voltage of the external power supply is adjusted to an appropriate value to electrically connect the third electrode terminal. The connected lithium source is forced to discharge, thereby replenishing lithium to the positive or negative electrode of the electrode assembly.

Next, the secondary battery of the present application will be described with reference to the drawings.

FIG. 1 is a schematic diagram of an embodiment of a secondary battery of the present application. FIG. 2 is an exploded schematic diagram of the secondary battery shown in FIG. 1 . As shown in FIGS. 1 and 2 , the secondary battery 5 includes a case 51 , an end cap assembly 53 and an electrode assembly 52 . FIG. 3 is an exploded schematic view of another embodiment of the secondary battery of the present application. As shown in FIG. 3 , the housing 51 has an opening, and the end cap assembly 53 is used to close the opening of the housing 51 , and the end cap assembly 53 is provided with a first electrode terminal 531 , a second electrode terminal 532 and a third electrode terminal 533 . The electrode assembly 52 is packaged in the casing 51 and electrically connected to the first electrode terminal 531 and the second electrode terminal 532 .

As shown in FIG. 3 , the secondary battery of the present application further includes a lithium source 54 disposed inside the housing 51 and electrically connected to the third electrode terminal 533 . As shown in FIG. 4 and FIG. 5 , the lithium source 54 includes a lithium metal layer 541 and a metal carrier 542 located between the lithium metal layer 541 and the casing 51 and used to support the lithium metal layer 541 .

In some embodiments, the lithium source is disposed inside the casing by welding, but the application is not limited thereto.

In some embodiments, the material of the metal carrier is not specifically limited. As an example, the material of the metal carrier may be selected from copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy or stainless steel. Optionally, the material of the metal carrier is selected from copper, copper alloy or stainless steel. The shape of the metal carrier is not specifically limited, and can be selected according to actual needs. For example, the metal carrier is a metal foil, or a metal mesh.

In some embodiments, the lithium metal layer may be selected from one or more of lithium powder, lithium ingot, and lithium sheet, but the application is not limited thereto. The lithium metal layer may be provided on the surface of the metal carrier by rolling, but the present application is not limited thereto.

As shown in FIG. 4 and FIG. 5 , in some embodiments, the housing 51 includes a bottom plate 511 and a side plate 512 , the side plate 512 is connected to the bottom plate 511 , and the bottom plate 511 and the side plate 512 are enclosed to form an accommodating cavity with an opening. The end cap assembly 53 is used to close the opening, so as to close the accommodating cavity, and encapsulate the electrode assembly (not shown) in the casing 51 .

In some embodiments, the lithium source is disposed inside the bottom plate and/or inside the side plates. As shown in FIG. 4 , in some embodiments, the lithium source 54 is disposed inside the bottom plate 511 . As shown in FIG. 5 , in some embodiments, the lithium source 54 is disposed inside the side plate 512 . Optionally, the lithium source is disposed inside the bottom plate. When the lithium source is arranged on the inner side of the side plate, the surface of the lithium source is parallel to the large surface of the electrode assembly. At this time, uneven lithium insertion at the winding tail of the electrode assembly is likely to occur; and when the lithium source is arranged on the inner side of the bottom plate, the lithium source The surface is parallel to the end face of the electrode assembly, so that the distance between the surface of the lithium source and each circle of electrode pole pieces of the electrode assembly is the same. lithium. At the same time, when the lithium source is arranged inside the bottom plate, the gravity of the electrode assembly can also be used to achieve good physical compression between the lithium metal layer and the metal carrier, ensuring good electronic conductivity between the lithium metal layer and the metal carrier.

As shown in FIG. 3 , in some embodiments, the secondary battery of the present application further includes an insulator 55 located between the lithium source 54 and the electrode assembly 52 to separate the lithium source 54 from the electrode assembly 52 . The type of the insulating member is not specifically limited, and any known porous film with good chemical stability and mechanical stability can be selected. For example, in some embodiments, the material of the porous membrane may be selected from one or more of glass fibers, non-woven fabrics, polyethylene, polypropylene, and polyvinylidene fluoride, but not limited thereto. The porous membrane can be a single-layer film or a multi-layer composite film. When the porous film is a multilayer composite film, the materials of each layer are the same or different.

As shown in FIG. 3 , in some embodiments, the end cover assembly 53 includes an end cover 534 that covers the opening of the housing 51 and is connected with the housing 51 , thereby closing the opening of the housing 51 . End cap 534 is generally flat plate shaped. In some embodiments, the end cover 534 is welded to the housing 51 , and the first electrode terminal 531 , the second electrode terminal 532 and the third electronic terminal 533 are fixed on the end cover 534 to form the end cover assembly 53 . One of the first electrode terminal and the second electrode terminal is a positive electrode terminal, and the other is a negative electrode terminal. The first electrode terminal and the second electrode terminal may also be provided with a connection member (not shown), or may also be referred to as a current collecting member, for electrically connecting the electrode assembly with the first electrode terminal and the second electrode terminal.

In some embodiments, the electrode assembly includes a positive pole piece and a negative pole piece, the positive pole piece is electrically connected to one of the first electrode terminal and the second electrode terminal and the negative pole piece is connected to the first electrode terminal and the second electrode terminal. The other one of them is electrically connected, so that the electrode assembly is electrically connected with the first electrode terminal and the second electrode terminal. The positive pole piece includes a positive current collector and a positive film layer disposed on at least one surface of the positive current collector and including positive active materials. For example, the positive electrode current collector has two opposite surfaces in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector. As an example, the positive electrode film layer is coated on the surface of the positive electrode collector, and the positive electrode collector without the positive electrode film layer protrudes from the positive electrode collector with the positive electrode film layer, and the positive electrode collector without the positive electrode film layer is used as Positive pole ear. The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including negative electrode active materials. For example, the negative electrode current collector has two opposite surfaces in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector. As an example, the negative electrode film layer is coated on the surface of the negative electrode collector, and the negative electrode collector without the negative electrode film layer protrudes from the negative electrode collector with the negative electrode film layer, and the negative electrode collector without the negative electrode film layer is used as Negative pole ear. In some embodiments, in order to ensure that a large current is passed without fusing, there are multiple positive tabs and stacked together, and multiple negative tabs are stacked together.

In some embodiments, the positive tab is electrically connected to one of the first electrode terminal and the second electrode terminal and the negative tab is electrically connected to the other of the first electrode terminal and the second electrode terminal, so that the electrodes The assembly is electrically connected with the first electrode terminal and the second electrode terminal. For example, the positive tabs of one or more electrode assemblies are electrically connected to one of the first electrode terminal and the second electrode terminal through a connecting member, and the negative tabs of one or more electrode assemblies are connected to the first electrode terminal through another connecting member. The one electrode terminal is electrically connected to the other of the second electrode terminals. As shown in FIG. 3 , the tab 521 is electrically connected to the first electrode terminal, and the tab 522 is electrically connected to the second electrode terminal. In some embodiments, the tab 521 is a positive tab, and the tab 522 is a negative tab; in other embodiments, the tab 521 is a negative tab, and the tab 522 is a positive tab.

In some embodiments, the positive pole piece and the negative pole piece can be made into an electrode assembly through a winding process or a lamination process.

The lithium metal layer in the lithium source is used to provide lithium ions that can migrate between the positive and negative electrodes. The quality of the lithium metal layer is not particularly limited and can be selected according to needs. In some embodiments, the ratio of the mass of the lithium metal layer to the total mass of the negative electrode active material is 0.001:1˜0.1:1. For example, the ratio of the mass of the lithium metal layer to the total mass of the negative active material is 0.001:1, 0.002:1, 0.005:1, 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06 :1, 0.07:1, 0.08:1, 0.09:1, 0.1:1 or the range formed by any of the above values. Optionally, the ratio of the mass of the lithium metal layer to the total mass of the negative electrode active material is 0.005:1˜0.03:1. The electrode assembly of the present application satisfies the above relationship, the quality of the lithium metal layer can meet the actual demand for lithium supplementation, and at the same time avoid the excessive quality of the lithium metal layer, causing most of the lithium to be idle and not used for lithium supplementation in the electrode assembly, which not only increases The production cost also reduces the mass energy density of the secondary battery.

In some embodiments, the capacity C1 per unit area of the negative electrode sheet and the capacity C2 per unit area of the positive electrode sheet satisfy C1/C2 of 1.0˜2.1. For example, C1/C2 is 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1 or any of the above ranges. Optionally, C1/C2 is 1.0-2.0, 1.0-1.9, 1.0-1.8, 1.0-1.7, 1.0-1.6, 1.0-1.5, 1.0-1.4 or 1.0-1.3. The capacity per unit area of the negative electrode sheet is greater than or equal to the capacity per unit area of the positive electrode sheet. During the charging and discharging process of the secondary battery, the vacancies provided by the negative electrode active material can fully accommodate the lithium ions from the lithium metal layer and the positive electrode active material. Interfacial lithium analysis.

In some embodiments, the total capacity C3 of the negative electrode sheet and the total capacity C4 of the positive electrode sheet satisfy C3/C4 of 1.0˜2.1. For example, C3/C4 is 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1 or any of the above ranges. Optionally, C3/C4 is 1.0-2.0, 1.0-1.9, 1.0-1.8, 1.0-1.7, 1.0-1.6, 1.0-1.5, 1.0-1.4 or 1.0-1.3. The total capacity of the negative electrode sheet is greater than or equal to the total capacity of the positive electrode sheet. During the charging and discharging process of the secondary battery, the vacancies provided by the negative electrode active material can fully accommodate the insertion of lithium ions from the lithium metal layer and the positive electrode active material, preventing the interface of the negative electrode from analysing. lithium.

In some embodiments, the total capacity C3 of the negative pole piece, the total capacity C4 of the positive pole piece, and the theoretical capacity C5 of the lithium metal layer satisfy C3/(C4+C5×K)≥0.2, where K represents the metal lithium in the lithium metal layer Used to compensate the utilization of lithium ions. For example, C3/(C4+C5×K) can be ≥0.3, ≥0.4, ≥0.5, ≥0.6, ≥0.7, ≥0.8, ≥0.9, ≥1.0, ≥1.1, ≥1.2, ≥1.3, ≥1.4, ≥1.5 , ≥1.6, ≥1.7 or ≥1.8. Optionally, C3/(C4+C5×K) is 0.5-1.8, 0.5-1.7, 0.5-1.6, 0.5-1.5, 0.5-1.4, 0.5-1.3, 0.5-1.2 or 0.5-1.1. The electrode assembly of the present application satisfies the above relationship and can effectively prevent lithium deposition at the interface of the negative electrode, thereby better improving the cycle performance, storage performance and safety performance of the secondary battery. The electrode assembly of the present application satisfies the above relationship, and the vacancies provided by the negative electrode active material in the negative electrode film layer can fully accommodate the insertion of all lithium ions from the lithium metal layer and the positive electrode active material, so as to realize the one-time insertion of lithium ions, and ensure that the negative electrode interface does not or, the negative electrode active material in the negative electrode film layer does not provide vacancies that can allow all lithium ions to be intercalated at one time, but it can ensure that during the charging and discharging process, storage process, and repair process of the secondary battery, by adjusting the external power supply Lithium is not separated at the interface of the negative electrode when the positive electrode or the negative electrode of the electrode assembly is supplemented with lithium.

In some embodiments, the total capacity C4 of the positive electrode sheet and the theoretical capacity C5 of the lithium metal layer satisfy (C5×K)/C4×100%≥3%. For example, (C5×K)/C4×100% can be ≥5%, ≥8%, ≥10%, ≥15%, ≥20%, ≥30%, ≥40%, ≥50%, ≥60%, ≥ 70%, ≥80%, ≥90%, or ≥100%. Optionally, (C5×K)/C4×100% is 5%˜100%. The electrode assembly of the present application satisfies the above relationship, the theoretical capacity of the lithium metal layer can meet the actual demand for lithium supplementation, avoiding the excessive mass of the lithium metal layer, causing most of the lithium to be idle and not used for lithium supplementation in the electrode assembly, which not only increases The production cost also reduces the mass energy density of the secondary battery.

In this application, the capacity C1 per unit area of the negative electrode sheet = the mass of the negative active material in the negative electrode sheet per unit area × the reversible gram capacity of the negative active material. The capacity C2 per unit area of the positive electrode sheet = the mass of the positive electrode active material in the positive electrode sheet per unit area × the reversible gram capacity of the positive electrode active material. The total capacity C3 of the negative electrode sheet=the total mass of the negative active material in the negative electrode sheet×the reversible gram capacity of the negative active material. The total capacity C4 of the positive electrode sheet = the total mass of the positive electrode active material in the positive electrode sheet × the reversible gram capacity of the positive electrode active material. The theoretical capacity C5 of the lithium metal layer=the total mass of metal lithium in the lithium metal layer×theoretical gram capacity of metal lithium.

In this application, the capacity C1 per unit area of the negative pole piece, the capacity C2 per unit area of the positive pole piece, the total capacity C3 of the negative pole piece, the total capacity C4 of the positive pole piece, and the theoretical capacity C5 of the lithium metal layer have the same unit, For example, both Ah or mAh. The "total mass of negative electrode active materials" means the total mass of all negative electrode active materials in the negative electrode sheet. When the negative electrode film layer is arranged on any one of the two opposite surfaces of the negative electrode current collector, the mass of the negative electrode active material in the negative electrode film layer is the total mass of the negative electrode active material. When the negative electrode film layer is arranged on two opposite surfaces of the negative electrode current collector, the sum of the mass of the negative electrode active material in each negative electrode film layer on the two opposite surfaces of the negative electrode current collector is the total mass of the negative electrode active material. The "total mass of positive electrode active materials" means the total mass of all positive electrode active materials in the positive electrode sheet. When the positive electrode film layer is arranged on any one of the two opposite surfaces of the positive electrode current collector, the mass of the positive electrode active material in the positive electrode film layer is the total mass of the positive electrode active material. When the positive electrode film layer is arranged on two opposite surfaces of the positive electrode current collector, the sum of the mass of the positive electrode active material in each positive electrode film layer on the two opposite surfaces of the positive electrode current collector is the total mass of the positive electrode active material.

In this application, the theoretical gram capacity of metal lithium is 3860mAh/g. Due to the fact that part of the metal lithium may be oxidized in the lithium metal layer and part of the metal lithium forms lithium ions to participate in the film formation of the negative electrode, the utilization rate K of the compensation lithium ions in the lithium metal layer is usually less than 100%, that is, K Indicates the percentage of the total amount of metal lithium that can actually be used to compensate lithium ions to the total amount of metal lithium initially set. According to research experience, the utilization rate K of the compensation lithium ions in the lithium metal layer is generally 75%-85%, for example 78%-82%, and for example 80%. Certainly, by reducing the oxidation of metal lithium in the lithium metal layer, and reducing metal lithium to form lithium ions to participate in negative electrode film formation, the utilization rate K can be increased.

In some embodiments, a secondary battery includes a case, a cap assembly, and an electrode assembly. The casing has an opening, the end cap assembly is used to close the opening of the casing, and the end cap assembly is provided with a first electrode terminal, a second electrode terminal and a third electrode terminal. The electrode assembly is packaged in the case and electrically connected with the first electrode terminal and the second electrode terminal. The secondary battery also includes a lithium source and an insulator, the lithium source is arranged inside the bottom plate of the case and is electrically connected to the third electrode terminal, and the lithium source includes a lithium metal layer and a lithium metal layer located between the lithium metal layer and the case for supporting lithium. The metal carrier of the metal layer, the insulator is located between the lithium source and the electrode assembly to separate the lithium source and the electrode assembly. The electrode assembly includes a positive pole piece and a negative pole piece. The ratio of the mass of the lithium metal layer to the total mass of the negative electrode active material is 0.001:1˜0.1:1. The capacity C1 per unit area of the negative pole piece and the capacity C2 per unit area of the positive pole piece satisfy C1/C2 of 1.0˜2.1. The total capacity C3 of the negative pole piece and the total capacity C4 of the positive pole piece satisfy C3/C4 of 1.0˜2.1. The total capacity C3 of the negative pole piece, the total capacity C4 of the positive pole piece and the theoretical capacity C5 of the lithium metal layer satisfy C3/(C4+C5×K)≥0.2. The total capacity C4 of the positive electrode sheet and the theoretical capacity C5 of the lithium metal layer satisfy (C5×K)/C4×100%≥3%.

In some embodiments, the positive electrode active material may include one or more of lithium transition metal oxides, olivine-structured lithium-containing phosphates and their respective modified compounds. In the secondary battery of the present application, the modification compounds of the above-mentioned positive electrode active materials may be modified by doping, surface coating, or surface coating while doping. As an example, the lithium transition metal oxide may include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, One or more of lithium nickel cobalt aluminum oxide and its modified compounds. As an example, the lithium-containing phosphate of olivine structure may include lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, lithium iron manganese phosphate and carbon One or more of the composite materials and their modified compounds. These positive electrode active materials may be used alone or in combination of two or more.

In some embodiments, the positive electrode active material includes one or more of olivine-structured lithium-containing phosphate and modified compounds thereof. Since lithium-containing phosphate with olivine structure has high structural stability, it will not cause capacity loss due to structural changes during secondary battery cycling like other positive electrode active materials, so lithium-containing phosphate with olivine structure is used The capacity fading of the secondary battery is mainly due to the loss of lithium ions that can migrate between the positive and negative electrodes inside the secondary battery. Therefore, after the third electrode terminal is electrically connected to the first electrode terminal or the second electrode terminal through an external power supply, the cycle performance and storage performance of the secondary battery can be greatly improved by supplementing the electrode assembly with lithium.

The positive film layer typically includes a positive active material and optionally a binder and an optional conductive agent. The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder and any other components in a solvent and stirring them uniformly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto. The type and content of the conductive agent and the binder are not specifically limited, and can be selected according to actual needs. As an example, the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene One or more of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. As an example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

The type of positive electrode current collector is not specifically limited, and can be selected according to actual needs. In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. As an example of the metal foil, aluminum foil may be used for the positive electrode current collector. The composite current collector may include a polymer material base and a metal material layer formed on at least one surface of the polymer material base. As an example, the metal material may be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may be selected from one or more of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, and the like.

In addition, in the secondary battery of the present application, the positive electrode sheet does not exclude other additional functional layers other than the positive electrode film layer. For example, in some embodiments, the positive electrode sheet described in the present application may further include a conductive primer layer (for example, composed of a conductive agent and a binder) disposed between the positive electrode current collector and the positive electrode film layer. In some other embodiments, the positive electrode sheet described in the present application further includes a protective layer covering the surface of the positive electrode film layer.

In some embodiments, the type of negative electrode active material is not specifically limited, and negative electrode active materials known in the art for secondary batteries may be used. As an example, the negative electrode active material may include one or more of graphite, soft carbon, hard carbon, mesocarbon microspheres, carbon fibers, carbon nanotubes, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials. The tin-based material may include one or more of simple tin, tin oxide, and tin alloy materials. The present application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials for secondary batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

The negative electrode film layer usually includes negative electrode active materials, optional binders, optional conductive agents and other optional additives. The negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing. The negative electrode slurry coating is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring them evenly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but not limited thereto. Wherein, the type and content of the conductive agent and the binder are not specifically limited, and can be selected according to actual needs. As an example, the conductive agent may include one or more of superconducting carbon, carbon black (such as acetylene black, ketjen black, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. As an example, the binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, polyacrylate sodium PAAS), polyacrylamide ( One or more of PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS). Other optional additives may include thickeners (such as sodium carboxymethylcellulose CMC-Na), PTC thermistor materials, and the like.

The type of the negative electrode collector is not specifically limited, and can be selected according to actual needs. In some embodiments, the negative electrode current collector may use a metal foil or a composite current collector. As an example of the metal foil, copper foil may be used for the negative electrode current collector. The composite current collector may include a polymer material base and a metal material layer formed on at least one surface of the polymer material base. As an example, the metal material may be selected from one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly One or more of ethylene (PE), etc.

In addition, in the secondary battery of the present application, the negative electrode sheet does not exclude other additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet described in the present application may further include a conductive primer layer (for example, composed of a conductive agent and a binder) disposed between the negative electrode current collector and the negative electrode film layer. In some other embodiments, the negative electrode sheet described in the present application further includes a protective layer covering the surface of the negative electrode film layer.

[Electrolyte]

The secondary battery of the present application also includes an electrolyte. The electrolyte plays the role of conducting active ions between the positive pole piece and the negative pole piece. The type of electrolyte is not specifically limited and can be selected according to requirements. For example, the electrolyte may be selected from at least one of solid electrolytes and liquid electrolytes (ie, electrolytic solutions).

In some embodiments, the electrolyte is an electrolytic solution. The electrolytic solution includes electrolyte salts and solvents.

In some embodiments, the type of electrolyte salt is not limited, and can be selected according to actual needs. As an example, the electrolyte salt may be selected from lithium hexafluorophosphate LiPF ₆ , lithium tetrafluoroborate LiBF ₄ , lithium perchlorate LiClO ₄ , lithium hexafluoroarsenate LiAsF ₆ , lithium bisfluorosulfonyl imide LiFSI, lithium trifluoromethanesulfonate LiTFS , lithium difluorooxalate borate LiDFOB, lithium difluorooxalate borate LiBOB, lithium difluorophosphate LiPO ₂ F ₂ , lithium difluorooxalate phosphate LiDFOP and lithium tetrafluorooxalate phosphate LiTFOP, LiN(SO ₂ RF) ₂ , LiN(SO ₂ F) One or more of (SO ₂ RF), wherein RF represents C _n F _2n+1 , and n is an integer of 1-10. Optionally, the electrolyte salt is selected from one or more of LiPF ₆ and LiN(SO ₂ RF) ₂ . Further, the electrolyte salt is selected from one or more of LiPF ₆ and lithium bistrifluoromethanesulfonimide LiTFSI.

In some embodiments, the type of solvent is not limited, and can be selected according to actual needs. As an example, the solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropylene carbonate ester (DPC), methyl propyl carbonate (MPC), ethylene propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA ), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), butyric acid One or more of ethyl ester (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE). In addition, the organic solvent may also include ionic liquids. The above-mentioned organic solvents may be used alone or in combination of two or more.

In some embodiments, additives are optionally included in the electrolyte. For example, additives can include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of batteries, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance. Additives etc.

[Isolation film]

Secondary batteries using electrolytes and some secondary batteries using solid electrolytes also include a separator. The separator is arranged between the positive pole piece and the negative pole piece to play the role of isolation. The type of the isolation membrane is not specifically limited, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.

In some embodiments, the material of the isolation film may be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, but not limited thereto. The isolation film can be a single-layer film or a multi-layer composite film. When the separator is a multilayer composite film, the materials of each layer are the same or different.

In some embodiments, a ceramic coating or a metal oxide coating may also be provided on the isolation film.

[Preparation]

The embodiment of the present application also provides a method for preparing a secondary battery, but the method for preparing the secondary battery of the present application is not limited thereto. An exemplary preparation method may include the following steps: making the positive electrode sheet and the negative electrode sheet into an electrode assembly through a winding process or a lamination process; placing a lithium source inside the casing with an opening, the lithium source includes a lithium metal layer and a A metal carrier between the lithium metal layer and the casing and used to support the lithium metal layer; the casing, the end cap assembly and the electrode assembly are assembled into a secondary battery. Wherein, the end cap assembly is provided with a first electrode terminal, a second electrode terminal and a third electrode terminal, the lithium source is electrically connected to the third electrode terminal, and the electrode assembly is electrically connected to the first electrode terminal and the second electrode terminal.

The preparation process of the secondary battery of the present application is simple and the production cost is low. After the third electrode terminal is electrically connected to the first electrode terminal or the second electrode terminal through an external power source, the lithium source can replenish lithium to the electrode assembly.

Lithium replenishment method for secondary battery

The second aspect of the embodiment of the present application provides a method for replenishing lithium in a secondary battery, the method at least including the following

steps

1 and 2.

Step 1, providing a secondary battery. A secondary battery includes a case, an end cap assembly, an electrode assembly, and a lithium source. The housing has an opening. The end cap assembly is used to close the opening of the housing and is provided with a first electrode terminal, a second electrode terminal and a third electrode terminal. The electrode assembly is packaged in the case and electrically connected with the first electrode terminal and the second electrode terminal. The lithium source is arranged inside the housing and is electrically connected to the third electrode terminal. The lithium source includes a lithium metal layer and a metal carrier located between the lithium metal layer and the housing and used to support the lithium metal layer.

In some embodiments, the secondary battery further includes an insulator between the lithium source and the electrode assembly to separate the lithium source from the electrode assembly.

In some embodiments, the housing includes a bottom plate and a side plate, the side plate is connected to the bottom plate, and the lithium source is disposed inside the bottom plate and/or inside the side plate. Optionally, the lithium source is disposed inside the bottom plate.

In some embodiments, the third electrode terminal is electrically connected to the negative pole of the external power supply, and the first electrode terminal or the second electrode terminal is electrically connected to the positive pole of the external power supply, so that the lithium source discharges to generate lithium ions and charge the electrode assembly Perform lithium supplementation.

Optionally, the external power supply is a charging and discharging motor.

Optionally, the adjustable range of the voltage of the external power supply is 0V-5V. When the voltage of the external power supply is 0V, it means that the electrode assembly is supplemented with lithium through the spontaneous voltage difference between the third electrode terminal and the first electrode terminal or the second electrode terminal.

In some embodiments, the current of the external power supply is 0.002A˜50A. Optionally, the current of the external power supply is 0.005A˜0.1A. Using a smaller current to replenish lithium to the electrode assembly can reduce the impact of concentration polarization on the uniformity of lithium replenishment, and using a smaller current to replenish lithium to the electrode assembly can improve the actual utilization of the lithium metal layer, which is conducive to accurate Precisely control the rate and amount of lithium supplementation during each lithium supplementation. When supplementing lithium during the charging and discharging process, storage process, repairing process, etc. of the secondary battery, it is preferable to fully charge the secondary battery, and then adjust the external power supply so that the lithium source discharges to generate lithium ions and supplement lithium to the electrode assembly. The amount of lithium replenishment can be the same as the decaying capacity of the secondary battery after cycling.

In some embodiments, the total capacity C3 of the negative electrode sheet and the total capacity C4 of the positive electrode sheet satisfy C3/C4 of 1.0˜2.1. Optionally, C3/C4 is 1.0-1.3.

In some embodiments, the total capacity C3 of the negative pole piece, the total capacity C4 of the positive pole piece, and the theoretical capacity C5 of the lithium metal layer satisfy C3/(C4+C5×K)≥0.2, where K represents the metal lithium in the lithium metal layer Used to compensate the utilization of lithium ions. Optionally, C3/(C4+C5×K) is 0.5˜1.1.

In some embodiments, the total capacity C4 of the positive electrode sheet and the theoretical capacity C5 of the lithium metal layer satisfy (C5×K)/C4×100%≥3%. Optionally, (C5×K)/C4×100% is 5%˜100%.

In some embodiments, the number of lithium supplementation to the electrode assembly is one or more times. The energizing current I ₁ and energizing time T ₁ of the external power supply and the total capacity C3 of the negative pole piece, the total capacity C4 of the positive pole piece, and the theoretical capacity C5 of the lithium metal layer satisfy C3/(C4+C5×K )≦C3/(C4+I ₁ ×T ₁ )<C3/C4, K represents the utilization rate of metal lithium in the lithium metal layer for compensating lithium ions. I ₁ ×T ₁ represents the theoretical capacity at each lithium supplementation. The measurement unit of I ₁ ×T ₁ is the same as the total capacity C3 of the negative electrode sheet, the total capacity C4 of the positive electrode sheet, and the theoretical capacity C5 of the lithium metal layer, for example, Ah or mAh.

The timing of lithium replenishment for the secondary battery of this application is not subject to specific restrictions, and can be selected according to actual needs. For example, the third electrode terminal is controllably electrically connected to the first electrode terminal or the second electrode terminal through an external power supply, so that it can be used in the secondary battery manufacturing process (for example, before the formation process, after the formation process), and in the secondary battery During the charging and discharging process, storage process, repair process, etc., the lithium source is used to supplement lithium to the electrode assembly according to actual needs. In some embodiments, when supplementing lithium in the secondary battery preparation process (for example, before the formation process, after the formation process), the current _I2 and the time _T2 of the external power supply are related to the total capacity C3, The total capacity C4 of the positive pole piece satisfies C3/(C4+I ₂ ×T ₂ )≧1.02. The electrode assembly of the present application satisfies the above relationship, and the vacancies provided by the negative electrode active material in the negative electrode film layer can fully accommodate the insertion of all lithium ions from the lithium metal layer and the positive electrode active material, so as to realize lithium ions during lithium supplementation in the secondary battery preparation process. It can be embedded at one time, and it is guaranteed that lithium will not be separated at the negative electrode interface. The measurement unit of I ₂ ×T ₂ is the same as the total capacity C3 of the negative electrode sheet and the total capacity C4 of the positive electrode sheet, for example, both are Ah or mAh.

The method for supplementing lithium according to the second aspect of the embodiment of the present application is used for supplementing lithium to the secondary battery according to the first aspect of the embodiment of the present application.

Battery modules and battery packs

In some embodiments of the present application, the secondary battery according to the present application can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

FIG. 6 is a schematic diagram of a battery module 4 as an example. As shown in FIG. 6 , in the battery module 4 , a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 . Of course, it can also be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

Optionally, the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.

In some embodiments of the present application, the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

7 and 8 are schematic diagrams of the battery pack 1 as an example. As shown in FIGS. 7 and 8 , the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 is used to cover the lower box body 3 and forms a closed space for accommodating the battery module 4 . Multiple battery modules 4 can be arranged in the battery box in any manner.

Electrical device

Embodiments of the present application further provide an electric device, the electric device includes at least one of the secondary battery, the battery module, and the battery pack of the present application. The secondary battery, battery module or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device. The electric device can be, but not limited to, mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

The electric device can select a secondary battery, a battery module or a battery pack according to its usage requirements.

FIG. 9 is a schematic diagram of an example electrical device. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the demand for high power and high energy density of the electric device, a battery pack or a battery module can be used.

As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, and the like. The electrical device is usually required to be light and thin, and a secondary battery can be used as a power source.

Example

The following examples describe the content disclosed in the present application more specifically, and these examples are for illustrative purposes only, since various modifications and changes within the scope of the disclosed content of the application will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods, and can be directly The instruments used without further processing, as well as in the examples, are commercially available.

Performance Testing

(1) Cycle performance test

At 60°C, charge the secondary battery with a constant current of 1C until the voltage is 3.65V, and then charge it with a constant voltage of 3.65V until the current is ≤0.05C. At this time, the secondary battery is fully charged. Record the charging capacity at this time. It is the charging capacity of the first cycle; after the secondary battery is left to stand for 5 minutes, it is discharged at a constant current of 1C to a voltage of 2.5V. This is a cyclic charge-discharge process. Record the discharge capacity at this time, which is the discharge capacity of the first cycle . The secondary battery was subjected to a cycle charge and discharge test according to the above method, and the discharge capacity after each cycle was recorded. The ratio of the discharge capacity after a certain number of cycles of the secondary battery to the discharge capacity of the first cycle is used to characterize the capacity retention rate of the secondary battery after a certain number of cycles.

(2) Storage performance test

At 25°C, charge the secondary battery at a constant current of 0.33C to a voltage of 3.65V, and then charge it at a constant voltage of 3.65V to a current of ≤0.05C; after standing the secondary battery for 5 minutes, discharge it at a constant current of 0.33C to The voltage is 2.5V, and the actual discharge capacity of the secondary battery is recorded as C ₀ . At 25°C, continue to charge the secondary battery with a constant current of 0.33C ₀ to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V to a current of ≤0.05C ₀ , and the secondary battery is fully charged. Store the fully-charged secondary battery in a thermostat at 60°C for a period of time and then take it out. After standing still for 5 minutes, discharge the secondary battery at a constant current of 0.33C to a voltage of 2.5V to obtain the stored discharge capacity. The ratio of the discharge capacity of the secondary battery after storage for a certain period of time to the actual discharge capacity of the secondary battery is C ₀ to characterize the capacity retention rate of the secondary battery after storage for a certain period of time.

Comparative example 1

Preparation of negative electrode sheet

Negative electrode active material artificial graphite (reversible gram capacity is 351mAh/g), conductive agent acetylene black, binder SBR, thickener CMC according to the mass ratio 96:2:1.8:1.6:0.4 in an appropriate amount of solvent deionized water fully Stirring and mixing to obtain negative electrode slurry; coating the negative electrode slurry on both surfaces of the copper foil of the negative electrode current collector, drying and cold pressing to obtain the negative electrode sheet. Wherein, the total mass of negative electrode active materials on both surfaces of the negative electrode sheet is 1000 g, and the coating weight of one side of the negative electrode slurry is 0.150 g/1540.25 mm ² (excluding solvent).

Preparation of positive electrode sheet

The positive electrode active material lithium iron phosphate (reversible gram capacity is 144mAh/g), the conductive agent acetylene black, and the binder PVDF are fully stirred and mixed in an appropriate amount of solvent NMP according to the mass ratio of 96:2:2 to obtain the positive electrode slurry; the positive electrode The slurry is coated on both surfaces of the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained after drying and cold pressing. Among them, the total mass of the positive electrode active material on both surfaces of the positive electrode sheet is 2152.8g, and the coating weight of one side of the positive electrode slurry is 0.323g/1540.25mm ² (excluding solvent).

Separator

A porous polyethylene film was used as the separator.

Electrolyte preparation

In an argon atmosphere glove box with a water content<10ppm, ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) are mixed according to a mass ratio of 1:1:1 to obtain an organic solvent; Fully dried LiPF ₆ is uniformly dissolved in the above organic solvent to obtain an electrolyte solution, wherein the concentration of LiPF ₆ is 1mol/L.

Preparation of secondary batteries

Stack and wind the above-mentioned positive pole piece, separator, and negative pole piece in order to obtain an electrode assembly; then put the electrode assembly into the case, add the above electrolyte, package through the end cap assembly, stand still, and form , capacity and other processes to obtain a secondary battery.

C1/C2=(0.150g/1540.25mm ² ×96%×351mAh/g)/(0.323g/1540.25mm ² ×96%×144mAh/g)=1.13.

C3/C4=(1000g×351mAh/g)/(2152.8g×144mAh/g)=1.13.

The discharge capacity of the secondary battery after 1500 cycles is 248.0Ah, and the capacity retention rate is 80.0%.

The discharge capacity of the secondary battery after storage for 300 days was 248.0 Ah, and the capacity retention rate was 80.0%.

Comparative example 2

The preparation method of the secondary battery is similar to Comparative Example 1, except that: the total mass of the negative electrode active material on both surfaces of the negative pole sheet is 1200g, and the single-sided coating weight of the negative electrode slurry is 0.180g/1540.25mm ² ( not including solvent); the total mass of positive electrode active materials on both surfaces of the positive electrode sheet is 2232g, and the coating weight of one side of the positive electrode slurry is 0.335g/1540.25mm ² (excluding solvent).

C1/C2=(0.180g/1540.25mm ² ×96%×351mAh/g)/(0.335g/1540.25mm ² ×96%×144mAh/g)=1.31.

C3/C4=(1200g×351mAh/g)/(2232g×144mAh/g)=1.31.

The discharge capacity of the secondary battery after 1500 cycles is 247.5Ah, and the capacity retention rate is 77.0%.

The discharge capacity of the secondary battery after storage for 300 days was 247.5 Ah, and the capacity retention rate was 77.0%.

Comparative example 3

The preparation method of the secondary battery is similar to Comparative Example 1, except that: the total mass of the negative electrode active material on both surfaces of the negative pole sheet is 1500g, and the single-sided coating weight of the negative electrode slurry is 0.225g/1540.25mm ² ( not including solvent); the total mass of the positive electrode active material on both surfaces of the positive electrode sheet is 2325g, and the coating weight of one side of the positive electrode slurry is 0.349g/1540.25mm ² (excluding solvent).

C1/C2=(0.225g/1540.25mm ² ×96%×351mAh/g)/(0.349g/1540.25mm ² ×96%×144mAh/g)=1.57.

C3/C4=(1500g×351mAh/g)/(2325g×144mAh/g)=1.57.

The discharge capacity of the secondary battery after 1500 cycles is 251.1 Ah, and the capacity retention rate is 75.0%.

The discharge capacity of the secondary battery after storage for 300 days was 251.1 Ah, and the capacity retention rate was 75.0%.

Example 1

The preparation method of the secondary battery is similar to Comparative Example 1, except that the preparation process of the secondary battery is adjusted.

Weld the lithium source on the inner side of the bottom plate of the shell; stack and wind the positive pole piece, separator, and negative pole piece in order to obtain the electrode assembly; then put the electrode assembly into the shell, add electrolyte, and pass through the end cap assembly After encapsulation, standing still, formation, capacity and other processes, the secondary battery is obtained. The end cover assembly is provided with a first electrode terminal, a second electrode terminal and a third electrode terminal, the first electrode terminal is electrically connected to the positive pole piece, the second electrode terminal is electrically connected to the negative pole piece, and the third electrode terminal is connected to the lithium source. The metal carrier is electrically connected. The metal carrier in the lithium source is copper foil (20 μm in thickness), and the lithium metal layer is obtained by uniformly rolling lithium foil (2 mm in thickness) on the copper foil, and the ratio of the mass of the lithium metal layer to the total mass of the negative electrode active material is 0.005:1.

C3/C4=(1000g×351mAh/g)/(2152.8g×144mAh/g)=1.13.

C3/(C4+C5×K)=(1000g×351mAh/g)/(2152.8g×144mAh/g+1000g×0.005×3860mAh/g×80%)=1.08.

(C5×K)/C4×100%=(1000g×0.005×3860mAh/g×80%)/(2152.8g×144mAh/g)×100%=5.0%.

The discharge capacity of the secondary battery is 248.00Ah after 1500 cycles, and then the third electrode terminal is electrically connected to the negative electrode of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive electrode of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 154.4h, and the theoretical capacity C6 of this lithium supplementation is 15.44Ah.

C3/(C4+C6)=(1000g×351mAh/g)/(2152.8g×144mAh/g+15.44×1000mAh)=1.08.

After lithium supplementation, charge the secondary battery with a constant current of 1C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V to a current ≤0.05C; let the secondary battery stand for 5 minutes, and discharge it at a constant current of 1C to a voltage of 2.5C V, the discharge capacity of the secondary battery was obtained to be 263.44Ah, and the capacity retention increased to 85.0%.

The discharge capacity of the secondary battery after storage for 300 days is 248.90Ah, after which the third electrode terminal is electrically connected to the negative pole of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive pole of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 154.4h, and the theoretical capacity C6 of this lithium supplementation is 15.44Ah.

C3/(C4+C6)=(1000g×351mAh/g)/(2152.8g×144mAh/g+15.44×1000mAh)=1.08.

After lithium supplementation, charge the secondary battery with a constant current of 0.33C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V until the current is ≤0.05C; after the secondary battery is left to stand for 5 minutes, discharge it at a constant current of 0.33C to a voltage of 3.65V The discharge capacity of the secondary battery is 2.5V, and the discharge capacity of the secondary battery is 264.34Ah, and the capacity retention rate increases to 85.3%.

Example 2

The preparation method of the secondary battery is similar to that of Example 1, except that the ratio of the mass of the lithium metal layer to the total mass of the negative electrode active material is 0.008:1.

C3/C4=(1000g×351mAh/g)/(2152.8g×144mAh/g)=1.13.

C3/(C4+C5×K)=(1000g×351mAh/g)/(2152.8g×144mAh/g+1000g×0.008×3860mAh/g×80%)=1.05.

(C5×K)/C4×100%=(1000g×0.008×3860mAh/g×80%)/(2152.8g×144mAh/g)×100%=8.0%.

The discharge capacity of the secondary battery is 248.3Ah after 1500 cycles, and then the third electrode terminal is electrically connected to the negative electrode of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive electrode of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 247h, and the theoretical capacity C6 of this lithium supplementation is 24.7Ah.

C3/(C4+C6)=(1000g×351mAh/g)/(2152.8g×144mAh/g+24.70×1000mAh)=1.05.

After lithium supplementation, charge the secondary battery with a constant current of 1C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V to a current ≤0.05C; let the secondary battery stand for 5 minutes, and discharge it at a constant current of 1C to a voltage of 2.5C V, the discharge capacity of the secondary battery was obtained to be 273.0Ah, and the capacity retention increased to 88.1%.

The discharge capacity of the secondary battery after storage for 300 days is 247.9Ah, after which the third electrode terminal is electrically connected to the negative pole of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive pole of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 247.0h, and the theoretical capacity C6 of this lithium supplementation is 24.70Ah.

C3/(C4+C6)=(1000g×351mAh/g)/(2152.8g×144mAh/g+24.70×1000mAh)=1.05.

After lithium supplementation, charge the secondary battery with a constant current of 0.33C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V until the current is ≤0.05C; after the secondary battery is left to stand for 5 minutes, discharge it at a constant current of 0.33C to a voltage of 3.65V The discharge capacity of the secondary battery is 2.5V, and the discharge capacity of the secondary battery is 272.6Ah, and the capacity retention rate increases to 87.9%.

Example 3

The preparation method of the secondary battery is similar to that of Example 1, except that the ratio of the mass of the lithium metal layer to the total mass of the negative electrode active material is 0.015:1.

C3/C4=(1000g×351mAh/g)/(2152.8g×144mAh/g)=1.13.

C3/(C4+C5×K)=(1000g×351mAh/g)/(2152.8g×144mAh/g+1000g×0.015×3860mAh/g×80%)=0.99.

(C5×K)/C4×100%=(1000g×0.015×3860mAh/g×80%)/(2152.8g×144mAh/g)×100%=14.9%.

The discharge capacity of the secondary battery is 248.90Ah after 1500 cycles, and then the third electrode terminal is electrically connected to the negative electrode of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive electrode of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium replenishment current is 0.1A, the lithium replenishment time is 463.2h, and the theoretical capacity C6 of this lithium replenishment is 46.32Ah.

C3/(C4+C6)=(1000g×351mAh/g)/(2152.8g×144mAh/g+46.32×1000mAh)=0.99.

After lithium supplementation, charge the secondary battery with a constant current of 1C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V to a current ≤0.05C; let the secondary battery stand for 5 minutes, and discharge it at a constant current of 1C to a voltage of 2.5C V, the discharge capacity of the secondary battery was obtained to be 295.22Ah, and the capacity retention increased to 95.2%.

The discharge capacity of the secondary battery after storage for 300 days is 248.70Ah. After that, the third electrode terminal is electrically connected to the negative electrode of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive electrode of the charge-discharge machine to discharge the lithium source to generate lithium ions. Lithium supplementation is performed on the electrode assembly. Among them, the lithium replenishment current is 0.1A, the lithium replenishment time is 463.2h, and the theoretical capacity C6 of this lithium replenishment is 46.32Ah.

C3/(C4+C6)=(1000g×351mAh/g)/(2152.8g×144mAh/g+46.32×1000mAh)=0.99.

After lithium supplementation, charge the secondary battery with a constant current of 0.33C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V until the current is ≤0.05C; after the secondary battery is left to stand for 5 minutes, discharge it at a constant current of 0.33C to a voltage of 3.65V is 2.5V, the discharge capacity of the secondary battery is 295.02Ah, and the capacity retention rate increases to 95.2%.

Example 4

The preparation method of the secondary battery is similar to that of Example 1, except that the ratio of the mass of the lithium metal layer to the total mass of the negative electrode active material is 0.03:1.

C3/C4=(1000g×351mAh/g)/(2152.8g×144mAh/g)=1.13.

C3/(C4+C5×K)=(1000g×351mAh/g)/(2152.8g×144mAh/g+1000g×0.03×3860mAh/g×80%)=0.87.

(C5×K)/C4×100%=(1000g×0.03×3860mAh/g×80%)/(2152.8g×144mAh/g)×100%=29.9%.

The discharge capacity of the secondary battery is 247.5Ah after 1500 cycles, and then the third electrode terminal is electrically connected to the negative electrode of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive electrode of the charge-discharge machine to discharge the lithium source to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 620h, and the theoretical capacity C6 of this lithium supplementation is 62Ah.

C3/(C4+C6)=(1000g×351mAh/g)/(2152.8g×144mAh/g+62×1000mAh)=0.94.

After lithium supplementation, charge the secondary battery with a constant current of 1C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V to a current ≤0.05C; let the secondary battery stand for 5 minutes, and discharge it at a constant current of 1C to a voltage of 2.5C V, the discharge capacity of the obtained secondary battery is 309.5Ah, and the capacity retention rate increases to 99.8%.

The discharge capacity of the secondary battery after storage for 300 days is 248.4Ah, after which the third electrode terminal is electrically connected to the negative pole of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive pole of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 620h, and the theoretical capacity C6 of this lithium supplementation is 62Ah.

C3/(C4+C6)=(1000g×351mAh/g)/(2152.8g×144mAh/g+62×1000mAh)=0.94.

After lithium supplementation, charge the secondary battery with a constant current of 0.33C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V until the current is ≤0.05C; after the secondary battery is left to stand for 5 minutes, discharge it at a constant current of 0.33C to a voltage of 3.65V The discharge capacity of the secondary battery is 2.5V, and the discharge capacity of the secondary battery is 310.4Ah, and the capacity retention rate increases to 100.1%.

Example 5

The preparation method of the secondary battery is similar to that of Example 1, except that the ratio of the mass of the lithium metal layer to the total mass of the negative electrode active material is 0.08:1.

C3/C4=(1000g×351mAh/g)/(2152.8g×144mAh/g)=1.13.

C3/(C4+C5×K)=(1000g×351mAh/g)/(2152.8g×144mAh/g+1000g×0.08×3860mAh/g×80%)=0.63.

(C5×K)/C4×100%=(1000g×0.08×3860mAh/g×80%)/(2152.8g×144mAh/g)×100%=79.7%.

The discharge capacity of the secondary battery is 247.7Ah after 1500 cycles, and then the third electrode terminal is electrically connected to the negative pole of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive pole of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 620h, and the theoretical capacity C6 of this lithium supplementation is 62Ah.

C3/(C4+C6)=(1000g×351mAh/g)/(2152.8g×144mAh/g+62×1000mAh)=0.94.

After lithium supplementation, charge the secondary battery with a constant current of 1C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V to a current ≤0.05C; let the secondary battery stand for 5 minutes, and discharge it at a constant current of 1C to a voltage of 2.5C V, the discharge capacity of the secondary battery was obtained to be 309.7Ah, and the capacity retention increased to 99.9%.

The discharge capacity of the secondary battery after storage for 300 days is 247.8Ah, after which the third electrode terminal is electrically connected to the negative pole of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive pole of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 620h, and the theoretical capacity C6 of this lithium supplementation is 62Ah.

C3/(C4+C6)=(1000g×351mAh/g)/(2152.8g×144mAh/g+62×1000mAh)=0.94.

After lithium supplementation, charge the secondary battery with a constant current of 0.33C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V until the current is ≤0.05C; after the secondary battery is left to stand for 5 minutes, discharge it at a constant current of 0.33C to a voltage of 3.65V The discharge capacity of the secondary battery is 2.5V, and the discharge capacity of the secondary battery is 309.8Ah, and the capacity retention rate increases to 99.9%.

Example 6

The preparation method of the secondary battery is similar to that of Example 1, except that the ratio of the mass of the lithium metal layer to the total mass of the negative electrode active material is 0.1:1.

C3/C4=(1000g×351mAh/g)/(2152.8g×144mAh/g)=1.13.

C3/(C4+C5×K)=(1000g×351mAh/g)/(2152.8g×144mAh/g+1000g×0.1×3860mAh/g×80%)=0.57.

(C5×K)/C4×100%=(1000g×0.1×3860mAh/g×80%)/(2152.8g×144mAh/g)×100%=99.6%.

The discharge capacity of the secondary battery is 248.0Ah after 1500 cycles, and then the third electrode terminal is electrically connected to the negative electrode of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive electrode of the charge-discharge machine to discharge the lithium source to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 620h, and the theoretical capacity C6 of this lithium supplementation is 62Ah.

C3/(C4+C6)=(1000g×351mAh/g)/(2152.8g×144mAh/g+62×1000mAh)=0.94.

After lithium supplementation, charge the secondary battery with a constant current of 1C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V to a current ≤0.05C; let the secondary battery stand for 5 minutes, and discharge it at a constant current of 1C to a voltage of 2.5C V, the discharge capacity of the secondary battery was obtained to be 310.0Ah, and the capacity retention increased to 100.0%.

The discharge capacity of the secondary battery after storage for 300 days is 248.5Ah, and then the third electrode terminal is electrically connected to the negative electrode of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive electrode of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 620h, and the theoretical capacity C6 of this lithium supplementation is 62Ah.

C3/(C4+C6)=(1000g×351mAh/g)/(2152.8g×144mAh/g+62×1000mAh)=0.94.

After lithium supplementation, charge the secondary battery with a constant current of 0.33C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V until the current is ≤0.05C; after the secondary battery is left to stand for 5 minutes, discharge it at a constant current of 0.33C to a voltage of 3.65V The discharge capacity of the secondary battery is 2.5V, and the discharge capacity of the secondary battery is 310.5Ah, and the capacity retention rate increases to 100.2%.

Example 7

The preparation method of the secondary battery is similar to that of Example 1, except that the lithium supplementation current is adjusted.

The discharge capacity of the secondary battery is 248.0Ah after 1500 cycles, and then the third electrode terminal is electrically connected to the negative electrode of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive electrode of the charge-discharge machine to discharge the lithium source to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium replenishment current is 0.3A, the lithium replenishment time is 51.5h, and the theoretical capacity C6 of this lithium replenishment is 15.44Ah.

C3/(C4+C6)=(1000g×351mAh/g)/(2152.8g×144mAh/g+15.44×1000mAh)=1.08.

After lithium supplementation, charge the secondary battery with a constant current of 1C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V to a current ≤0.05C; let the secondary battery stand for 5 minutes, and discharge it at a constant current of 1C to a voltage of 2.5C V, the discharge capacity of the secondary battery was obtained to be 252.96Ah, and the capacity retention increased to 81.6%.

The discharge capacity of the secondary battery after storage for 300 days is 248.0Ah, after which the third electrode terminal is electrically connected to the negative pole of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive pole of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium replenishment current is 0.3A, the lithium replenishment time is 51.5h, and the theoretical capacity C6 of this lithium replenishment is 15.44Ah.

C3/(C4+C6)=(1000g×351mAh/g)/(2152.8g×144mAh/g+15.44×1000mAh)=1.08.

After lithium supplementation, charge the secondary battery with a constant current of 0.33C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V until the current is ≤0.05C; after the secondary battery is left to stand for 5 minutes, discharge it at a constant current of 0.33C to a voltage of 3.65V is 2.5V, the discharge capacity of the secondary battery is 252.34Ah, and the capacity retention rate increases to 81.4%.

Example 8

The preparation method of the secondary battery is similar to that of Example 1, except that the total mass of the negative electrode active material on both surfaces of the negative electrode sheet is 1200g, and the single-sided coating weight of the negative electrode slurry is 0.180g/1540.25mm ² ( Not including solvent); The total mass of the positive active material on both surfaces of the positive electrode sheet is 2232g, and the single-side coating weight of the positive electrode slurry is 0.335g/1540.25mm ² (not including solvent); the quality of the lithium metal layer is the same as that of the negative electrode The ratio of the total mass of active materials was 0.005.

C3/C4=(1200g×351mAh/g)/(2232g×144mAh/g)=1.31.

C3/(C4+C5×K)=(1200g×351mAh/g)/(2232g×144mAh/g+1200g×0.005×3860mAh/g×80%)=1.24.

(C5×K)/C4×100%=(1200g×0.005×3860mAh/g×80%)/(2232g×144mAh/g)×100%=5.8%.

The discharge capacity of the secondary battery is 247.48Ah after 1500 cycles, and then the third electrode terminal is electrically connected to the negative electrode of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive electrode of the charge-discharge machine to discharge the lithium source to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium replenishment current is 0.1A, the lithium replenishment time is 185.3h, and the theoretical capacity C6 of this lithium replenishment is 18.53Ah.

C3/(C4+C6)=(1200g×351mAh/g)/(2232g×144mAh/g+18.53×1000mAh)=1.24.

After lithium supplementation, charge the secondary battery with a constant current of 1C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V to a current ≤0.05C; let the secondary battery stand for 5 minutes, and discharge it at a constant current of 1C to a voltage of 2.5C V, the discharge capacity of the secondary battery was obtained to be 266.01Ah, and the capacity retention increased to 82.8%.

The discharge capacity of the secondary battery after storage for 300 days is 247.48Ah, after which the third electrode terminal is electrically connected to the negative pole of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive pole of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium replenishment current is 0.1A, the lithium replenishment time is 185.3h, and the theoretical capacity C6 of this lithium replenishment is 18.53Ah.

C3/(C4+C6)=(1200g×351mAh/g)/(2232g×144mAh/g+18.53×1000mAh)=1.24.

After lithium supplementation, charge the secondary battery with a constant current of 0.33C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V until the current is ≤0.05C; after the secondary battery is left to stand for 5 minutes, discharge it at a constant current of 0.33C to a voltage of 3.65V The discharge capacity of the secondary battery is 2.5V, and the discharge capacity of the secondary battery is 266.01Ah, and the capacity retention rate increases to 82.8%.

Example 9

The preparation method of the secondary battery is similar to that of Example 8, except that the ratio of the mass of the lithium metal layer to the total mass of the negative electrode active material is 0.008:1.

C3/C4=(1200g×351mAh/g)/(2232g×144mAh/g)=1.31.

C3/(C4+C5×K)=(1200g×351mAh/g)/(2232g×144mAh/g+1200g×0.008×3860mAh/g×80%)=1.20.

(C5×K)/C4×100%=(1200g×0.008×3860mAh/g×80%)/(2232g×144mAh/g)×100%=9.2%.

The discharge capacity of the secondary battery is 247.2Ah after 1500 cycles. After that, the third electrode terminal is electrically connected to the negative electrode of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive electrode of the charge-discharge machine to discharge the lithium source to generate lithium ions. Lithium supplementation is performed on the electrode assembly. Among them, the lithium replenishment current is 0.1A, the lithium replenishment time is 296.4h, and the theoretical capacity C6 of this lithium replenishment is 29.64Ah.

C3/(C4+C6)=(1200g×351mAh/g)/(2232g×144mAh/g+29.64×1000mAh)=1.20.

After lithium supplementation, charge the secondary battery with a constant current of 1C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V to a current ≤0.05C; let the secondary battery stand for 5 minutes, and discharge it at a constant current of 1C to a voltage of 2.5C V, the discharge capacity of the secondary battery was obtained to be 276.84Ah, and the capacity retention increased to 86.1%.

The discharge capacity of the secondary battery after storage for 300 days is 246.9Ah, after which the third electrode terminal is electrically connected to the negative pole of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive pole of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium replenishment current is 0.1A, the lithium replenishment time is 296.4h, and the theoretical capacity C6 of this lithium replenishment is 29.64Ah.

C3/(C4+C6)=(1200g×351mAh/g)/(2232g×144mAh/g+29.64×1000mAh)=1.20.

After lithium supplementation, charge the secondary battery with a constant current of 0.33C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V until the current is ≤0.05C; after the secondary battery is left to stand for 5 minutes, discharge it at a constant current of 0.33C to a voltage of 3.65V The discharge capacity of the secondary battery is 2.5V, and the discharge capacity of the secondary battery is 276.54 Ah, and the capacity retention rate increases to 86.0%.

Example 10

The preparation method of the secondary battery is similar to that of Example 8, except that the ratio of the mass of the lithium metal layer to the total mass of the negative electrode active material is 0.015:1.

C3/C4=(1200g×351mAh/g)/(2232g×144mAh/g)=1.31.

C3/(C4+C5×K)=(1200g×351mAh/g)/(2232g×144mAh/g+1200g×0.015×3860mAh/g×80%)=1.12.

(C5×K)/C4×100%=(1200g×0.015×3860mAh/g×80%)/(2232g×144mAh/g)×100%=17.3%.

The discharge capacity of the secondary battery is 247.5Ah after 1500 cycles, and then the third electrode terminal is electrically connected to the negative electrode of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive electrode of the charge-discharge machine to discharge the lithium source to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 555.8h, and the theoretical capacity C6 of this lithium supplementation is 55.58Ah.

C3/(C4+C6)=(1200g×351mAh/g)/(2232g×144mAh/g+55.58×1000mAh)=1.12.

After lithium supplementation, charge the secondary battery with a constant current of 1C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V to a current ≤0.05C; let the secondary battery stand for 5 minutes, and discharge it at a constant current of 1C to a voltage of 2.5C V, the discharge capacity of the secondary battery was obtained to be 303.08Ah, and the capacity retention increased to 94.3%.

The discharge capacity of the secondary battery after storage for 300 days is 247.3Ah, after which the third electrode terminal is electrically connected to the negative pole of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive pole of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 555.8h, and the theoretical capacity C6 of this lithium supplementation is 55.58Ah.

C3/(C4+C6)=(1200g×351mAh/g)/(2232g×144mAh/g+55.58×1000mAh)=1.12.

After lithium supplementation, charge the secondary battery with a constant current of 0.33C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V until the current is ≤0.05C; after the secondary battery is left to stand for 5 minutes, discharge it at a constant current of 0.33C to a voltage of 3.65V The discharge capacity of the secondary battery is 2.5V, and the discharge capacity of the secondary battery is 302.88Ah, and the capacity retention rate increases to 94.2%.

Example 11

The preparation method of the secondary battery is similar to that of Example 1, except that the total mass of the negative electrode active material on both surfaces of the negative electrode sheet is 1500g, and the single-side coating weight of the negative electrode slurry is 0.225g/1540.25mm ² ( Not including solvent); The total mass of the positive active material on both surfaces of the positive electrode sheet is 2325g, and the single-sided coating weight of the positive electrode slurry is 0.349g/1540.25mm ² (not including solvent); the quality of the lithium metal layer is the same as that of the negative electrode The ratio of the total mass of active materials is 0.005:1.

C3/C4=(1500g×351mAh/g)/(2325g×144mAh/g)=1.57.

C3/(C4+C5×K)=(1500g×351mAh/g)/(2325g×144mAh/g+1500g×0.005×3860mAh/g×80%)=1.47.

(C5×K)/C4×100%=(1500g×0.005×3860mAh/g×80%)/(2325g×144mAh/g)×100%=6.9%.

The discharge capacity of the secondary battery is 251.0Ah after 1500 cycles, and then the third electrode terminal is electrically connected to the negative electrode of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive electrode of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 231.6h, and the theoretical capacity C6 of this lithium supplementation is 23.16Ah.

C3/(C4+C6)=(1500g×351mAh/g)/(2325g×144mAh/g+23.16×1000mAh)=1.47.

After lithium supplementation, charge the secondary battery with a constant current of 1C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V to a current ≤0.05C; let the secondary battery stand for 5 minutes, and discharge it at a constant current of 1C to a voltage of 2.5C V, the discharge capacity of the secondary battery was obtained to be 274.16Ah, and the capacity retention increased to 81.9%.

The discharge capacity of the secondary battery after storage for 300 days is 251.1Ah, after which the third electrode terminal is electrically connected to the negative pole of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive pole of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 231.6h, and the theoretical capacity C6 of this lithium supplementation is 23.16Ah.

C3/(C4+C6)=(1500g×351mAh/g)/(2325g×144mAh/g+23.16×1000mAh)=1.47.

After lithium supplementation, charge the secondary battery with a constant current of 0.33C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V until the current is ≤0.05C; after the secondary battery is left to stand for 5 minutes, discharge it at a constant current of 0.33C to a voltage of 3.65V The discharge capacity of the secondary battery is 2.5V, and the discharge capacity of the secondary battery is 274.26Ah, and the capacity retention rate increases to 81.9%.

Example 12

The preparation method of the secondary battery is similar to that of Example 11, except that the ratio of the mass of the lithium metal layer to the total mass of the negative electrode active material is 0.008:1.

C3/C4=(1500g×351mAh/g)/(2325g×144mAh/g)=1.57.

C3/(C4+C5×K)=(1500g×351mAh/g)/(2325g×144mAh/g+1500g×0.008×3860mAh/g×80%)=1.42.

(C5×K)/C4×100%=(1500g×0.008×3860mAh/g×80%)/(2325g×144mAh/g)×100%=11.1%.

The discharge capacity of the secondary battery is 251.1Ah after 1500 cycles, and then the third electrode terminal is electrically connected to the negative electrode of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive electrode of the charge-discharge machine to discharge the lithium source to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 370.6h, and the theoretical capacity C6 of this lithium supplementation is 37.06Ah.

C3/(C4+C6)=(1500g×351mAh/g)/(2325g×144mAh/g+37.06×1000mAh)=1.42.

After lithium supplementation, charge the secondary battery with a constant current of 1C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V to a current ≤0.05C; let the secondary battery stand for 5 minutes, and discharge it at a constant current of 1C to a voltage of 2.5C V, the discharge capacity of the secondary battery was obtained to be 288.16Ah, and the capacity retention increased to 86.1%.

The discharge capacity of the secondary battery after storage for 300 days is 250.4Ah, after which the third electrode terminal is electrically connected to the negative pole of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive pole of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 370.6h, and the theoretical capacity C6 of this lithium supplementation is 37.06Ah.

C3/(C4+C6)=(1500g×351mAh/g)/(2325g×144mAh/g+37.06×1000mAh)=1.42.

After lithium supplementation, charge the secondary battery with a constant current of 0.33C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V until the current is ≤0.05C; after the secondary battery is left to stand for 5 minutes, discharge it at a constant current of 0.33C to a voltage of 3.65V The discharge capacity of the secondary battery is 287.46h, and the capacity retention rate increases to 85.9%.

Example 13

The preparation method of the secondary battery is similar to that of Example 11, except that the ratio of the mass of the lithium metal layer to the total mass of the negative electrode active material is 0.015:1.

C3/C4=(1500g×351mAh/g)/(2325g×144mAh/g)=1.57.

C3/(C4+C5×K)=(1500g×351mAh/g)/(2325g×144mAh/g+1500g×0.015×3860mAh/g×80%)=1.30.

(C5×K)/C4×100%=(1500g×0.015×3860mAh/g×80%)/(2325g×144mAh/g)×100%=20.8%.

The discharge capacity of the secondary battery is 251.1Ah after 1500 cycles, and then the third electrode terminal is electrically connected to the negative electrode of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive electrode of the charge-discharge machine to discharge the lithium source to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 694.8h, and the theoretical capacity C6 of this lithium supplementation is 69.48Ah.

C3/(C4+C6)=(1500g×351mAh/g)/(2325g×144mAh/g+69.48×1000mAh)=1.30.

After lithium supplementation, charge the secondary battery with a constant current of 1C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V to a current ≤0.05C; let the secondary battery stand for 5 minutes, and discharge it at a constant current of 1C to a voltage of 2.5C V, the discharge capacity of the secondary battery was obtained to be 320.58Ah, and the capacity retention increased to 95.8%.

The discharge capacity of the secondary battery after storage for 300 days is 251.4Ah, after which the third electrode terminal is electrically connected to the negative pole of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive pole of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 694.8h, and the theoretical capacity C6 of this lithium supplementation is 69.48Ah.

C3/(C4+C6)=(1500g×351mAh/g)/(2325g×144mAh/g+69.48×1000mAh)=1.30.

After lithium supplementation, charge the secondary battery with a constant current of 0.33C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V until the current is ≤0.05C; after the secondary battery is left to stand for 5 minutes, discharge it at a constant current of 0.33C to a voltage of 3.65V The discharge capacity of the secondary battery is 2.5V, and the discharge capacity of the secondary battery is 320.88Ah, and the capacity retention rate increases to 95.8%.

Example 14

The preparation method of the secondary battery is similar to that of Example 13, except that the lithium source is welded on the inner side of the casing side plate.

C3/C4=(1500g×351mAh/g)/(2325g×144mAh/g)=1.57.

(C5×K)/C4×100%=(1500g×0.015×3860mAh/g×80%)/(2325g×144mAh/g)×100%=20.8%.

C3/(C4+C6)=(1500g×351mAh/g)/(2325g×144mAh/g+69.48×1000mAh)=1.30.

After lithium supplementation, charge the secondary battery with a constant current of 1C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V to a current ≤0.05C; let the secondary battery stand for 5 minutes, and discharge it at a constant current of 1C to a voltage of 2.5C V, the discharge capacity of the secondary battery was obtained to be 312.04Ah, and the capacity retention increased to 93.2%.

The discharge capacity of the secondary battery after storage for 300 days is 251.8Ah, after which the third electrode terminal is electrically connected to the negative pole of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive pole of the charge-discharge machine, so that the lithium source is discharged to generate lithium ions Lithium supplementation is performed on the electrode assembly. Among them, the lithium supplementation current is 0.1A, the lithium supplementation time is 694.8h, and the theoretical capacity C6 of this lithium supplementation is 694.8Ah.

C3/(C4+C6)=(1500g×351mAh/g)/(2325g×144mAh/g+69.48×1000mAh)=1.30.

After lithium supplementation, charge the secondary battery with a constant current of 0.33C to a voltage of 3.65V, and then charge it with a constant voltage of 3.65V until the current is ≤0.05C; after the secondary battery is left to stand for 5 minutes, discharge it at a constant current of 0.33C to a voltage of 3.65V The discharge capacity of the secondary battery is 2.5V, and the discharge capacity of the secondary battery is 311.44Ah, and the capacity retention rate increases to 93.0%.

Example 15

The preparation method of the secondary battery is similar to that of Example 1, except that the timing of lithium supplementation is different, and the ratio of the mass of the lithium metal layer to the total mass of the negative electrode active material is 0.0024:1.

After the secondary battery is formed, the third electrode terminal is electrically connected to the negative electrode of the charge-discharge machine, and the second electrode terminal is electrically connected to the positive electrode of the charge-discharge machine, so that the lithium source discharges to generate lithium ions and replenish lithium to the electrode assembly. Among them, the lithium replenishment current is 0.1A, the lithium replenishment time is 74.1h, and the theoretical capacity C6 of this lithium replenishment is 7.41Ah.

C3/(C4+C6)=(1000g×351mAh/g)/(2152.8g×144mAh/g+7.41×1000mAh)=1.11.

C3/C4=(1000g×351mAh/g)/(2152.8g×144mAh/g)=1.13.

C3/(C4+C5×K)=(1000g×351mAh/g)/(2152.8g×144mAh/g+1000g×0.0024×3860mAh/g×80%)=1.11.

(C5×K)/C4×100%=(1000g×0.0024×3860mAh/g×80%)/(2152.8g×144mAh/g)×100%=2.4%.

The capacity retention rate of the secondary battery after 1500 cycles is 81.7%, and the capacity retention rate after 300 days of storage is 81.6%.

Table 1 The performance test results of the secondary battery prepared in Comparative Examples 1-3

序号serial number	循环1500圈后的容量保持率Capacity retention rate after 1500 cycles	存储300天后的容量保持率Capacity retention after 300 days of storage
对比例1Comparative example 1	80.0％80.0%	80.0％80.0%
对比例2Comparative example 2	77.0％77.0%	77.0％77.0%
对比例3Comparative example 3	75.0％75.0%	75.0％75.0%

Table 2 Parameters and test results of lithium supplementation after 1500 cycles of secondary batteries prepared in Examples 1-14

Table 3 The parameters and test results of lithium supplementation after the secondary batteries prepared in Examples 1-14 were stored for 300 days

Table 4 Parameters and test results of lithium supplementation after formation of the secondary battery prepared in Example 15

From the test results of Table 1 to Table 4, it can be seen that the secondary battery structure of the present application can control the rate and amount of lithium supplementation, thereby avoiding the occurrence of excessive lithium supplementation; Lithium supplementation is performed according to actual needs during the process and storage process, so that the secondary battery of the present application also has significantly improved cycle performance and storage performance.

The above is only a specific embodiment of the application, but the scope of protection of the application is not limited thereto. Any person familiar with the technical field can easily think of various equivalents within the scope of the technology disclosed in the application. Modifications or replacements, these modifications or replacements shall be covered within the scope of protection of this application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

A secondary battery comprising:

a housing having an opening;

an end cap assembly for closing the opening of the housing; and

An electrode assembly, packaged in the casing and including a positive pole piece and a negative pole piece;

in,

The end cap assembly is provided with a first electrode terminal, a second electrode terminal and a third electrode terminal,

the electrode assembly is electrically connected to the first electrode terminal and the second electrode terminal,

The secondary battery further includes a lithium source, the lithium source is disposed inside the case and electrically connected to the third electrode terminal, the lithium source includes a lithium metal layer and is located between the lithium metal layer and the between the shells and for supporting the metal carrier of the lithium metal layer,

The third electrode terminal is controllably electrically connected to the first electrode terminal or the second electrode terminal through an external power source, so that the lithium source can replenish lithium to the electrode assembly.
The secondary battery according to claim 1, wherein the casing comprises a bottom plate and a side plate, the lithium source is arranged inside the bottom plate and/or inside the side plate, optionally, the lithium source set on the inner side of the bottom plate.
The secondary battery according to claim 1 or 2, wherein the material of the metal carrier is selected from copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy or stainless steel.
The secondary battery according to any one of claims 1-3, wherein the secondary battery further comprises an insulating member between the lithium source and the electrode assembly.
The secondary battery according to any one of claims 1-4, wherein the total capacity C3 of the negative electrode sheet and the total capacity C4 of the positive electrode sheet satisfy C3/C4 of 1.0 to 2.1, optionally , C3/C4 is 1.0 to 1.3.
The secondary battery according to claim 5, wherein the total capacity C3 of the negative pole piece, the total capacity C4 of the positive pole piece, and the theoretical capacity C5 of the lithium metal layer satisfy C3/(C4+C5× K) ≥ 0.2, optionally, C3/(C4+C5×K) is 0.5˜1.1, K represents the utilization rate of metal lithium in the lithium metal layer for compensating lithium ions.
The secondary battery according to claim 6, wherein the total capacity C4 of the positive pole piece and the theoretical capacity C5 of the lithium metal layer satisfy (C5×K)/C4×100%≥3%, optionally , (C5×K)/C4×100% is 5% to 100%.
A lithium replenishing method for a secondary battery, at least comprising the steps of:

Step 1, providing a secondary battery, the secondary battery comprising:

a housing having an opening;

an end cap assembly for closing the opening of the housing and provided with a first electrode terminal, a second electrode terminal and a third electrode terminal;

an electrode assembly packaged in the case and electrically connected to the first electrode terminal and the second electrode terminal; and

a lithium source, disposed inside the casing and electrically connected to the third electrode terminal, including a lithium metal layer and a metal between the lithium metal layer and the casing and used to support the lithium metal layer carrier;

Step 2, electrically connecting the third electrode terminal to the first electrode terminal or the second electrode terminal through an external power source, so that the lithium source can replenish lithium to the electrode assembly.
The method of claim 8, wherein the secondary battery further comprises an insulator between the lithium source and the electrode assembly.
The method according to claim 8 or 9, wherein the housing comprises a bottom plate and a side plate, the lithium source is arranged inside the bottom plate and/or inside the side plate, optionally, the lithium A source is disposed inside the base plate.
The method according to any one of claims 8-10, wherein,

The external power supply is a charging and discharging motor, and/or,

The adjustable range of the voltage of the external power supply is 0V-5V.
The method according to any one of claims 8-11, wherein the energizing current of the external power supply is 0.002A-50A, optionally 0.005A-0.1A.
A battery module comprising the secondary battery according to any one of claims 1-7.
A battery pack comprising the battery module according to claim 13.
An electrical device, comprising at least one of the secondary battery according to any one of claims 1-7, the battery module according to claim 13, and the battery pack according to claim 14.